Scion 13101-21070 Piston Sub-Assy, W/Pin

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Clean the backs of the big-end bearing shells, and the recesses in the connecting rods and big-end caps. If new shells are being fitted, ensure that all traces of the protective grease are cleaned off using paraffin. Wipe the shells and connecting rods dry with a lint-free cloth. Lubricate No 1 piston and piston rings, and check that the ring gaps are spaced. Fit the connecting rod bearing shells in place, making sure the shell's locating tab engages correctly. Fit a ring compressor to No 1 piston, then insert the piston and connecting rod into No 1 cylinder. Make sure that the dot on the piston crown is facing the timing end of the engine. With No 1 crankpin at its lowest point, drive the piston carefully into the cylinder with the wooden handle of a hammer, at the same time guiding the connecting rod onto the crankpin. Press the big-end bearing shells into the connecting rod caps, aligning each shell with its locating groove. Liberally lubricate the crankpin journals and big-end bearing shells. Refit the bearing caps, which have dowels to ensure correct positioning. Tighten the new bearing cap bolts to the specified torque and angles, and turn the crankshaft each time to make sure that it is free before moving on to the next assembly.

By cleaning it off using paraffin.

Remove the cylinder head, sump, and oil pump pick-up tube, as applicable. Rotate the crankshaft so that No 1 big-end cap (timing chain end of the engine) is at the lowest point of its travel. If the big-end cap and rod are not already numbered, mark them with a marker pen. Mark both cap and rod to identify the cylinder they operate in. Unscrew and remove the big-end bearing cap bolts, and withdraw the cap complete with shell bearing from the connecting rod. Make sure that the shell remains in the cap and if necessary identify it for position. Discard the bolts -they are 'stretch' type, and should not be re-used. If only the bearing shells are being attended to, push the connecting rod up and off the crankpin, and remove the upper bearing shell. Keep the bearing shells and cap together in their correct sequence if they are to be refitted. If the piston is being removed, push the connecting rod up and remove the piston and rod from the top of the bore. Note that if there is a pronounced wear ridge at the top of the bore, there is a risk of damaging the piston as the rings foul the ridge. However, it is reasonable to assume that a rebore and new pistons will be required in any case if the ridge is so pronounced. Repeat the procedure for the remaining piston/connecting rod assemblies. Ensure that the caps and rods are marked before removal, as described previously, and keep all components in order. Mark the connecting rod and cap for position, and store together.

Before beginning the inspection process, the piston/connecting rod assemblies must be cleaned and the original piston rings removed. Carefully expand the old rings over the top of the pistons using two or three old feeler blades to prevent them from dropping into empty grooves. Scrape away carbon deposits from the top of the piston using a hand-held wire brush or fine emery cloth. Clean the ring grooves in the piston by using an old ring to remove carbon deposits, being careful not to scratch the sides or remove any metal. Clean the piston/connecting rod assembly with paraffin or a suitable solvent and ensure the oil return holes in the ring grooves are clear. If the pistons and cylinder bores are not excessively worn or damaged, the original pistons can be re-used, but new piston rings should always be used when reassembling the engine. Inspect each piston for cracks around the skirt, gudgeon pin bosses, and piston ring lands. Look for scoring, scuffing, holes, and burned areas on the piston. Scorch marks indicate improper sealing of the rings, while a hole in the piston crown suggests abnormal combustion. Correct any issues causing these problems. Corrosion in the form of small pits indicates coolant leakage, which must be addressed. Measure the piston ring-to-groove clearance and piston-to-bore clearance to determine if new pistons are required. Check the fit of the gudgeon pin and ensure there is no excessive play. Before refitting the rings, check their end gaps and install them correctly, spacing the top ring gaps at 180° to each other and positioning the oil control ring top and bottom rails correctly.

The ring grooves in the piston should be cleaned by using an old ring to remove carbon deposits, taking care not to scratch the sides or remove any metal.

The caps and rods should be marked for position before removal and stored together.